Continuous Ice Nuclei Measurements Made During Pulsed Cloud Seeding

Charles E. Robertson E. Bollay Associates, Inc., Boulder, Colo.

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Abstract

In a cloud seeding program, it is necessary to know what meteorological conditions are controlling the travel of artificial ice nuclei. While it is obvious that they will travel with the air currents, it is difficult to determine if the currents will travel to the desired area, and how much time is taken to transport the nuclei from the generator to the target area. Silver iodide particles were generated in a cyclic manner from ground-based generators, while continuous observations of ice nuclei were made on the surface in the target area. Observations show the surface wind velocity at the generator site to be the primary factor controlling the particle travel. However, nuclei concentrations have been observed to remain low even though the wind velocity was favorable for detection. This may be due to the silver iodide particles nucleating the cloud to form ice crystals, which do not enter the nucleus counter.

Abstract

In a cloud seeding program, it is necessary to know what meteorological conditions are controlling the travel of artificial ice nuclei. While it is obvious that they will travel with the air currents, it is difficult to determine if the currents will travel to the desired area, and how much time is taken to transport the nuclei from the generator to the target area. Silver iodide particles were generated in a cyclic manner from ground-based generators, while continuous observations of ice nuclei were made on the surface in the target area. Observations show the surface wind velocity at the generator site to be the primary factor controlling the particle travel. However, nuclei concentrations have been observed to remain low even though the wind velocity was favorable for detection. This may be due to the silver iodide particles nucleating the cloud to form ice crystals, which do not enter the nucleus counter.

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